Clinical studies of cystic fibrosis, a generalized inherited disease have been conducted with a view to defining more precisely some of the abnormalities that contribute to the pulmonary and gastrointestinal symptoms of this disease. An effort has also been made to refine selected diagnostic procedures and some of the measures used in the treatment of this condition. Definition was sought of the role of neutrophils in the derangements of the bronchial wall characteristic of CF by determining some of the neutrophil enzymes in the fluid obtained by broncho-pulmonary lavage by fiber-optic bronchoscopy. Studies of lingual lipase activity were conducted in order to further clarify the role of this enzyme in the absorption of fats in patients with CF. Serum amylase studies were aimed at evaluating the usefulness of different methods to determine this enzyme and its isoenzymes for diagnostic purposes. Cimetidine was administered on a long term basis to patients with CF in order to improve their fat and nitrogen absorption. Studies were also performed by pelvic ultrasonography to determine the size, presence and frequency of ovarian cysts.